A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Randall Morrow
Date: 2014 Sep 30, 11:46 -0700
The square mirror gives 2 edges at 90 degrees to help line up the levels properly. My metal base is round because the metal scrap I had was round. I have a plastic base that's rectangular and both work fine. The longer cylindrical levels give more range of bubble movement that gives accuracy and is easier for the eye to visualize. Search under Bill Morris here for a more scholarly talk on levels.